(北京航空航天大学 材料科学与工程系，北京 100083)
摘 要: 探讨了双态组织TiAl基合金中晶粒尺度对合金常温拉伸塑性的影响。对等温锻造后的γ TiAl基合金进行了热处理，获得了含有不同等轴γ晶粒及片层晶粒体积比的双态组织。采用单轴拉伸实验，对断口进行分析发现：双态组织的断裂方式是脆性断裂，在片层区域以穿晶解理断裂为主，而在以等轴γ区域为主的细晶区以沿晶断裂为主。通过统计断裂力学分析，建立了双态组织TiAl基合金拉伸塑性模型，并得出结论： 只有在晶粒半径细化到50μm以下，才会对拉伸塑性产生较大的影响。
关键字: TiAl基合金； 双态组织； 拉伸塑性； 晶粒尺度； 微裂纹
TiAl alloy with duplex structure
（Department of Materials Science and Engineering，
Beijing University Aeronautics & Astronautics， Beijing 100083，P.R.China）
Abstract:The effects of grain size on the tensile ductility in a TiAl alloy with duplex structure have been studied. Isothermally forged γ-TiAl alloy was heat treated， and a series of fine duplex microstructures with different volume fraction of equiaxed γ grains and lamellar colonies (α2+γ) were achieved. Uniaxial tension experiment was carried out at room temperature. Fracture surfaces analysis shows that the fracture mode of duplex structure is brittle fracture. In lamellar area， the fracture is dominated by transgranular cleavage， while in equiaxed γ grain area， intergranular decohesion is the main mode of failure. On the basis of an analysis of statistical fracture mechanics， a tensile ductility model of the TiAl alloy with duplex structure was established. And a conclusion is obtained that grain size has prominent effect on tensile ductility of this material only when the grain radius is refined to below 50μm.
Key words: TiAl alloys； duplex structure； tensile ductility； grain size； microcrack
